The lack of obvious genotypic-phenotypic correlation, as well as the inter- and intrafamilial clinical heterogeneity, even among carriers of the same CARMIL2 variant, seems to point towards a contribution of additional environmental, genetic, or epigenetic-modifying factors in determining the clinical manifestations of CARMIL2 deficiency. This evidence concerns the gene CARMIL2 and hyperinsulinemic hypoglycemia, familial, 4.